Environmental Chemicals Bad for Sperm
SAN FRANCISCO—Three chemicals that are used in manufacturing and wind up in the environment may significantly decrease sperm motility and viability, new findings suggest.
The chemicals, bisphenol A (BPA), 4-octylphenol, and phthalic acid, also can induce DNA damage, investigators reported here at the annual meeting of the American Society for Reproductive Medicine.
Canada already has banned the use of BPA in the manufacture of baby bottles, but the chemical is still used widely in a host of products. BPA is a chemical component of plastics found in food and beverage containers, as well as dental sealants. Studies have shown that in the body, BPA affects cells and tissues in much the same way estrogen does. A study by the CDC revealed the presence of urinary BPA in 93% of a U.S. reference population.
The researchers, Chinedu Nwabuobi, a medical student at the Albert Einstein College of Medicine in the Bronx, N.Y., and a colleague, Kazim Chohan, MD, at Upstate Medical University in Syracuse, N.Y., suspect that some cases of unexplained male fertility may be associated with BPA.
For their investigation, they incubated washed sperm samples from 21 men in different concentrations of these three chemicals. Sperm motility was evaluated at the start of incubation and at 30-minute intervals for two hours, and sperm viability was evaluated after one and two hours of incubation.
BPA showed the strongest negative effect on sperm motility and viability. Moreover, DNA damage in treated sperm was significantly greater compared with untreated sperm; BPA induced more sperm DNA damage than either 4-octylphenol or phthalic acid.
“These chemicals, when improperly disposed of, tend to end up in our water reservoirs and actually in our rivers and lakes,” said study investigator Mr. Nwabuobi. “[Because] these chemicals are also in cosmetics, and there can be [a resultant] accumulation.”
Despite the negative effects on sperm in vitro, preliminary findings of another study presented at the ASRM conference suggest the absence of an association between urinary BPA concentrations and semen parameters. The study included 71 male partners of couples seen at the Massachusetts General Hospital rertility center in Boston. The researchers said their finding “should be interpreted cautiously due to the small sample size.”
ASRM President G. David Adamson, MD, observed: “As levels of contaminants increase in the environment, they increase in our bodies. Estrogen-mimicking chemicals like BPA have potential to cause damage. These studies are beginning. More research is needed to fully define the effects of BPA and to understand its mechanisms.”